This invention relates to methods and optical systems for illuminating a target. The present invention also relates to methods and systems for performing sample assays, and for producing and measuring optical responses and signatures.
Targets, such as areas where optically transduced chemical and/or biochemical assays are performed, may need to be illuminated by a light source. It is often desirable to illuminate the target with light having enhanced uniformity of intensity over the entire target region. Optical signals are typically a function of the illumination intensity and, the more an illumination intensity varies across a target, the more the optical signal will also vary. The resultant variance in optical signals may be undesirable.
However, it can be difficult to efficiently provide illumination having enhanced or a high degree of uniformity. For example, lasers, which are commonly used for illuminating targets, typically have an intensity profile that is peaked at its center and which drops off radially towards the edges. This intensity profile is often a Gaussian, or bell shaped, profile. Therefore, if a target is directly illuminated with such a laser, the illumination of the target will not have a constant intensity. Rather, the center portion of the target will receive greater illumination intensity than the perimeter areas.
Therefore, there is a need for an apparatus and method to illuminate a target or selected area with enhanced uniformity as compared to directly illuminating the target with a given light source. Further, there is a need for an apparatus and method that provides enhanced illumination uniformity for optical targets such as those in chemical and/or biochemical assay systems.
According to certain embodiments of the invention, an apparatus is provided to illuminate a target. The apparatus comprises a light source, a first lens, a diffractive optical element, and a second lens. The first lens is configured to receive light from the light source. The diffractive optical element is configured to receive the light from the first lens and to regulate the light into regulated light. The second lens is configured to receive the regulated light and to direct the regulated light onto a selected area of the target.
According to certain embodiments of the invention, a method is provided to illuminate a target. The method comprises generating light from a light source, directing the light with a first lens to a diffractive optical element, generating regulated light with the diffractive optical element, and focusing the regulated light with a second lens onto a selected area of the target.
According to yet another aspect of the present invention, the inventive apparatus and method provide non-normal angle of incidence illumination of a selected area with a given light source with a greater degree of uniformity than is achieved when that light source is used to directly illuminate the selected area at the same non-normal angle of incidence.
According to certain embodiments of the present invention, the inventive apparatus and method are directed towards the analysis of a sample in which light is generated from a light source, the light is directed with a first lens to a diffractive optical element; regulated light is generated with the diffractive optical element; the regulated light is delivered onto a selected area of a target that comprises at least one optically active species; and changes in an optical signature of the at (east one optically active species are detected.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.